In the oil and gas industry, it is common to connect an electrical cable with one or more electrical instruments which are located or which are intended to be located downhole in a borehole such as a wellbore. The one or more electrical instruments may form a tool string which may be suspended from the electrical cable in the borehole.
The electrical cable is typically connected with the tool string by a cable connection system. The cable connection system typically provides both a mechanical connection and an electrical connection between the electrical cable and the tool string.
The cable connection system may include a housing. The housing may be comprised of a cable head or some other structure which is connected with the tool string and the electrical instruments, or the housing may be integrated into the tool string and/or into one or more of the electrical instruments.
Similar cable connection systems may be used to connect electrical cables with each other (i.e., to splice electrical cables) and/or to connect electrical cables with structures other than tool strings and electrical instruments (such as wellhead equipment).
The electrical cable typically comprises an electrical conductor (including one or more separate electrical wires), an electrical insulating material (including one or more layers of insulation), and a protective sheath.
The protective sheath protects the electrical conductor and the insulating material from the harsh downhole environments.
In some cases, the protective sheath may be comprised of a metal jacket which encapsulates the conductor and the insulating material. The metal jacket may be constructed of any suitable metal material or combination of metal materials including, as non-limiting examples, stainless steel or a metal alloy which can withstand downhole environments. A metal jacketed electrical cable is sometimes referred to as “tubewire”, “metal encapsulated cable”, “tubing encapsulated cable”, or similar names.
Examples in the prior art of connections between electrical cables and downhole electrical instruments can be found in U.S. Pat. No. 5,833,490 (Bouldin), U.S. Pat. No. 6,362,428 (Pennington), U.S. Pat. No. 7,980,873 (Emerson), U.S. Pat. No. 8,246,371 (Emerson), and U.S. Pat. No. 8,297,345 (Emerson).
There remains a need in the art for connections for metal jacketed electrical cables, and for methods for providing such connections.